The invention relates to a gear pump according to the preamble of claim 1.
In gear pumps of the generic type, the temperature of the bearing is of decisive importance for the maximally admissible speed and thus for the throughput of the pump. Plain bearings being customarily lubricated by the pumping medium, high energy feed is occasioned in the bearing clearance in the case of highly viscous pumping media. Since the pumping medium has a maximally admissible maximum temperature, the speed and thus the throughput of the gear pump are limited. This is of special importance when the pumping medium is plastic melt, the maximally admissible temperatures of which range from 300 to 350xc2x0 C.
EP 0 715 078 A2 describes a gear pump of the generic type which has cooling ducts meandering in the plain bearing.
EP 0 607 999 B1 teaches to provide the shaft of the gear rotors with cooling ducts.
The invention is based on the knowledge that the development of heat in the plain bearing varies along the circumference thereof and over the extension thereof in the direction of the central longitudinal axis.
It is an object of the invention to embody a gear pump of the generic type for optimal heat removal in the plain bearing.
Customarily, the highest energy feed is occasioned at the place of most reduced bearing clearance i.e., the clearance between the bearing section of the shaft and the area of the bearing shell called plain bearing; this is the place of maximum shearing of the highly viscous pumping medium. This is where mechanical energy is converted into heat energy to an especially high degree. Very thorough cooling is required in this area.
The sub-claims reflect numerous advantageous and partially inventive embodiments.